---
title: "Agent composability standards: which AI agents support MCP, A2A, Agent Skills and AGENTS.md (2026)"
url: https://agentcomposability.com/standards
description: "The open standards layer for composable AI agents, and a dated matrix of which agents support Agent Skills, AGENTS.md, MCP extensions and A2A. Every cell cites an official source."
last_checked: 2026-10-21
license: CC BY 4.0
---

# The standards, and who supports them

Composable parts need shared interfaces. This page lists the open standards for each layer of an agent system, and a dated matrix of which agents an official source lists for each standard.

## The open standards that make agents composable

Composable parts need shared interfaces. The Agentic AI Foundation (AAIF) names five layers of an “open agentic stack”, and one of its projects covers each layer. The Linux Foundation hosts the AAIF.

The table adds Agent Skills, two MCP extensions, and projects for discovery and conformance testing.

### The five AAIF layers

| Layer | Standard | Steward and status | Sources |
|---|---|---|---|
| Instructions and context | AGENTS.md | OpenAI released it in August 2025. OpenAI gave it to the AAIF when the AAIF formed on 9 December 2025. | [AAIF formation announcement](https://aaif.io/news/linux-foundation-announces-formation-of-aaif); [AAIF: A2A joins AAIF](https://aaif.io/blog/a2a-joins-aaif) |
| Agent runtime | goose | Block gave it to the AAIF on 9 December 2025. | [AAIF formation announcement](https://aaif.io/news/linux-foundation-announces-formation-of-aaif); [AAIF: A2A joins AAIF](https://aaif.io/blog/a2a-joins-aaif) |
| Agent to tool connectivity | Model Context Protocol (MCP) | Anthropic released it as open source in November 2024. Anthropic gave it to the AAIF on 9 December 2025. | [AAIF formation announcement](https://aaif.io/news/linux-foundation-announces-formation-of-aaif); [AAIF: A2A joins AAIF](https://aaif.io/blog/a2a-joins-aaif) |
| Traffic mediation and control | agentgateway | An AAIF project. It sits between agent systems and their infrastructure, and it manages routing, policy and observability. | [AAIF: A2A joins AAIF](https://aaif.io/blog/a2a-joins-aaif) |
| Agent to agent interoperability | Agent2Agent (A2A) | Google launched it in April 2025 and gave it to the Linux Foundation. It joined the AAIF as a hosted project on 17 August 2026. More than 150 organizations back it. | [AAIF: A2A joins AAIF](https://aaif.io/blog/a2a-joins-aaif) |

### Skills and MCP extensions

| Layer | Standard | Steward and status | Sources |
|---|---|---|---|
| Packaged procedures | Agent Skills | A skill is a folder with a SKILL.md file. Anthropic first developed the format and released it as an open standard. | [Agent Skills overview](https://agentskills.io/home) |
| Skills inside MCP | Skills over MCP extension (`io.modelcontextprotocol/skills`) | The specification has Final status. The Skills Over MCP Working Group maintains it. Hosts and software development kits are still adding support. | [MCP Skills extension](https://modelcontextprotocol.io/extensions/skills/overview) |
| Interactive interfaces inside MCP | MCP Apps extension (`io.modelcontextprotocol/ui`) | An extension to the core MCP specification. MCP servers can return interactive interfaces, such as forms and dashboards, that show in the chat. Host support varies by client. | [MCP Apps overview](https://modelcontextprotocol.io/extensions/apps/overview) |

### Discovery

| Layer | Standard | Steward and status | Sources |
|---|---|---|---|
| Find MCP servers | Official MCP Registry | In preview. The official central metadata repository for publicly accessible MCP servers. | [The MCP Registry](https://modelcontextprotocol.io/registry/about) |
| Find MCP servers | GitHub MCP Registry | GitHub launched it on 16 September 2025 as a place to discover MCP servers. | [The GitHub Blog](https://github.blog/ai-and-ml/github-copilot/meet-the-github-mcp-registry-the-fastest-way-to-discover-mcp-servers/) |
| Find A2A agents and MCP servers | AGNTCY directories | Cisco released AGNTCY as open source in March 2025. The Linux Foundation welcomed the project on 29 July 2025. Its directories make A2A agents and MCP servers discoverable. | [Linux Foundation press release](https://www.linuxfoundation.org/press/linux-foundation-welcomes-the-agntcy-project-to-standardize-open-multi-agent-system-infrastructure-and-break-down-ai-agent-silos) |

### Conformance testing

| Layer | Standard | Steward and status | Sources |
|---|---|---|---|
| Test MCP clients and servers | MCP Conformance Test Framework | Tests MCP client and server implementations against the specification. | [modelcontextprotocol/conformance](https://github.com/modelcontextprotocol/conformance) |
| Test A2A implementations | A2A Technology Compatibility Kit (TCK) | A compatibility test suite for A2A implementations on three transports. | [a2aproject/a2a-tck](https://github.com/a2aproject/a2a-tck) |

## Which agents support which standards

The matrix shows which agents each official source lists. The matrix covers six agents: Claude Code, ChatGPT and Codex, Cursor, GitHub Copilot with Visual Studio Code (VS Code), Gemini CLI (command-line interface) and goose.

Each column names its source and the date of the last check. In the A2A column, each cell cites the documentation of that client.

- **Listed**: An official source names the client as supporting the standard.
- **Listed, partial**: The source names the client and labels its support “Partial”.
- **Not listed**: The source that we checked does not name the client. This makes no claim either way.

| Client | Agent Skills | AGENTS.md | MCP Apps | Skills over MCP | A2A |
|---|---|---|---|---|---|
| Claude Code | [Listed](https://agentskills.io/clients) (2026-10-21) | [Listed](https://code.claude.com/docs/en/memory#agents-md) (2026-10-21) | [Not listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://code.claude.com/docs/en/overview) (2026-10-21) |
| ChatGPT and Codex | [Listed](https://agentskills.io/clients) (2026-10-21) | [Listed](https://agents.md/) (2026-10-21) | [Listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Listed, partial](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://learn.chatgpt.com/docs) (2026-10-21) |
| Cursor | [Listed](https://agentskills.io/clients) (2026-10-21) | [Listed](https://agents.md/) (2026-10-21) | [Listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://cursor.com/docs) (2026-10-21) |
| GitHub Copilot and VS Code | [Listed](https://agentskills.io/clients) (2026-10-21) | [Listed](https://agents.md/) (2026-10-21) | [Listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://docs.github.com/en/copilot) (2026-10-07) |
| Gemini CLI | [Listed](https://agentskills.io/clients) (2026-10-21) | [Listed](https://agents.md/) (2026-10-21) | [Not listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Listed](https://geminicli.com/docs/core/remote-agents/) (2026-10-21) |
| goose | [Listed](https://agentskills.io/clients) (2026-10-21) | [Listed](https://agents.md/) (2026-10-21) | [Listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://modelcontextprotocol.io/extensions/client-matrix) (2026-10-21) | [Not listed](https://goose-docs.ai/docs/quickstart/) (2026-10-07) |

Data with the source and check date of every cell: [matrix.json](https://agentcomposability.com/matrix.json).

## Composability, orchestration and chaining

People often use these three words as if they mean the same thing. They do not.

Composability is a design property. Orchestration and chaining are runtime patterns: they describe how the parts run.

- **Composability** (Design property): You build the system from independent units. You can swap or recombine the units. Sources: [Atlan](https://atlan.com/know/ai-agent/agent-composability/).
- **Orchestration** (Runtime pattern): A central agent breaks a task into parts while it runs. It gives the parts to worker agents and combines their results. It suits tasks with subtasks that you cannot predict. Sources: [Atlan](https://atlan.com/know/ai-agent/agent-composability/); [Anthropic](https://www.anthropic.com/engineering/building-effective-agents).
- **Chaining** (Runtime pattern): The steps run in a fixed sequence. The output of each step is the input of the next step. It suits workflows that you can predict. Sources: [Atlan](https://atlan.com/know/ai-agent/agent-composability/); [Anthropic](https://www.anthropic.com/engineering/building-effective-agents).

Composability makes both runtime patterns possible. Atlan gives an example: units with clean boundaries “can be chained today and orchestrated tomorrow without a rewrite.”

## How this page stays true

- We check each source by hand.
- Each matrix cell uses one official source: the list that the standard publishes, or the documentation of the client.
- Each cell records its source and the date of its last check. When a source changes, we change the cell and its date.